centering round disc ?

1/8" thick 4" diameter steel circle. has a 1" hole in center.

I want to stack many of these and drill holes in them.

How can I get these disks to center on the rotary index table?

Someone had this idea:

use lathe to taper 1" round stock to a point. The point is center. Put this in the center of the rotary index table (it has a small indentation at center). Drill a 1" hole in a

1/2" thick piece of steel. lay this on top of the index table, with the 1" tapered round piece going through the hole. The taper goes through the clamp "ways" on the rotary index table. The 1/2 " steel is to keep the tapered 1" rod 90 degrees to the table.

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Reply to
aiiadict
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What and where are the holes you need to drill?

Reply to
Tom Gardner

Hi,

thanks for reply,

Holes need to be drilled on outer diameter of the metal discs, 4 of them. They all need to be 1.5" from the center of the discs, at

0,90,180,270 degrees (a square)

problem is the discs have a 1" hole in their center, so a compass cannot be used to locate the center of the holes that need to be drilled.

I don't know what to measure off of.

I will go upload drawings to dropbox now.

Thanks, Rich

Reply to
aiiadict

My thought would be to make a jig for drilling. A piece of metal maybe 1/2 inch thick with a 1 inch shaft in the center which would center the disc. Then four drill bushings in the right places.

No rotary table required for use. Just drop the jig over the disc. Drill the first hole. drop in pin so disc does not turn, Drill three remaining holes.

Dan

Reply to
dcaster

If the discs are really round, and if the holes don't have to be super-precise, then the way I'd do this is:

(trig moment)

chord length L inscribed in a circle of diameter D with an angle ALPHA: L = D * SIN(ALPHA/2)

Disc is 4" diameter, angle is 90°, sin(45°) = 0.707: L = 2.828"

Set dividers to 2.828", ink discs, step off 3 times, check that 4th step exactly returns to first mark (if not, adjust calipers slightly, reink and iterate) until you've accurately divided the circumference into quarters. Then draw diameters through your marks, lay out your holes, centerpunch, and punch out the holes on an ironworker. Take lots longer to do the layout than to punch the holes, but still MUCH faster than drilling on RT.

GWE

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Reply to
Grant Erwin

If your lathe is an Atlas, you could chuck a stack of washers in the

3-jaw and use the index pin in the bull gear to locate the hole location. Mount drill on toolpost.

- - Rex Burkheimer

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Reply to
Rex B

A pic isn't necessary to solve this riddle. Make a simple aluminum holding fixture that has a 1" pin that protrudes upwards, long enough to locate as many pieces as you'd like to drill at one time. There should be enough thickness of the fixture to allow you to drill through the bottom part completely, but not drill into your table. SET A STOP so you can't drill too deep. This setup will locate your parts on center with no setup time. The pin in the fixture should also plug into the hole in the rotary table (or index head), automatically centering itself with the table. All you need do is locate the centerline of the table/index head as it relates to the spindle (which you do by the use of a DTI, before inserting the fixture, or by dialing the pin afterwards), then step off the radius. A couple finger clamps will hold the parts while you're drilling them. By dialing the table concentric with the spindle, you "measure" off the centerline of the setup, which in turn relates to the centerline of the parts. Clear? If not, ask questions.

Harold

Reply to
Harold and Susan Vordos

If I had to do this: Assumptions: 4 pieces, +/- 1/32" or better

*MIG tack weld the 4 together *Use centering head on a scale and scribe a diameter line on top disk *Prick the first and oposite hole at .5" from the OD on the diameter line. *Set your divider/compass to 2.12132" swing the divider/compass from both pricks to mark the other holes. Prick and follow with a bigger centerpunch. *Use a combined drill/countersink or center drill then follow with drills up to size. *Grind open the weld to free the disks.

Reply to
Tom Gardner

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